My experience with a 3:44 R&P and the 3-4 gap I could never find a place to sit, so you drove faster or slower to accommodate. The crusing speed was nice though.
So you will need to add A fifth gear but still turning at 3K when cruising to keep the engine cool and I experienced that with a 901 tranny with a 2332 engine in an IM speedster. It was a nice combo.
With the need to be at 3K RPM just to keep the car cooled, this makes even a 5th gear difficult if you are trying to get an old car to behave like a new car and that is more quietly or with less engine noise. It won't happen.
I was seriously thinking of a Berg-5 with my 2110cc IM, that was before I built new with full subie. Hope this helps.